how to create a loop for a macro?

[Danah Abdul]

I have a very large dataset but to cut it short I demonstrated the data with the following example:

* Example generated by -dataex-. To install: ssc install dataex
clear
input float(patid death dateofdeath)
 1 0     .
 2 0     .
 3 0     .
 4 0     .
 5 1 15007
 6 0     .
 7 0     .
 8 1 15526
 9 0     .
10 0     .
end
format %d dateofdeath

I am trying to sample for a case-control study based on date of death. At this stage, I need to first create a variable with each date of death repeated for all the participants (hence we end up with a dataset with 20 participants) and a "pairid" equivalent to the patient id (patid) of the corresponding case.

I created a macro for one case (which works) but finding it difficult to have it repeated for all cases (where death==1) in a loop.

The successful macro is as follows:

local i "5" //patient id who died
          
            gen pairid= `i'
            gen matchedindexdate = dateofdeath
            replace matchedindexdate=0 if pairid != patid
            gsort matchedindexdate
            replace matchedindexdate= matchedindexdate[_N]
            save temp`i'

and the loop I attempted is:

forval j = 1/10 (min and max patid id) {
count if patid == `j' & death==1 //to specify that I want the loop run for cases only.
if r(N)=1 {
            gen pairid= `j'
            gen matchedindexdate = dateofdeath
            replace matchedindexdate=0 if pairid != patid
            gsort matchedindexdate
            replace matchedindexdate= matchedindexdate[_N]
            save temp/matched`j'

}

}

use temp/matched1, clear
forval i=2/10 {
    capture append using temp/matched`i'
    save matched, replace
}

but I get

invalid syntax

How can I do the loop?

Your help is highly appreciated.

[Nick Cox]

Cross-posted at https://stackoverflow.com/questions/...macro-in-stata

 
 if r(N)=1 {

should be

 
 if r(N)==1 {

[Danah Abdul]

Nick Cox
Thank you for your reply.
I changed the command as recommended to

if r(N)==1 {

but I keep getting

invalid syntax

[Ali Atia]

You also need to comment out or remove the line that says (min and max patid id)

[Danah Abdul]

Ali Atia

yes thank you, it did work out, but not completely!!
My commands are now are:

forval j = 1/10 {
count if patid == `j' & death==1
if r(N)==1 {
gen pairid= `j'
gen matchedindexdate = dateofdeath
replace matchedindexdate=0 if pairid != patid
gsort matchedindexdate
replace matchedindexdate= matchedindexdate[_N]
save temp/matched`j'

}

}

use temp/matched1, clear
forval i=2/10 {
capture append using temp/matched`i'
save matched, replace
}

However, I am getting

variable pairid already defined

I do get the file matched5 afterwards with what I want but only for one case (for patid 5) but not for the other case (patid 8).

[Danah Abdul]

I got it solved!!! Many thanks for all those who helped.

I had to use the dataset again within the loop so this is how the final commands look like:

forval j = 1/10 {
use miniset,clear //this is the dataset example I am using.
count if patid == `j' & death==1
if r(N)==1 {
gen pairid= `j'
gen matchedindexdate = dateofdeath
replace matchedindexdate=0 if pairid != patid
gsort matchedindexdate
replace matchedindexdate= matchedindexdate[_N]
save temp/matched`j'



}

}


use temp/matched5, clear
forval i=6/10 {
capture append using temp/matched`i'
save matched, replace
}

Thank you again for all the help.